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The JavaScript 1.1 Array
I'm including the JavaScript 1.1 methods for working with arrays
here for those older applications that will some day require
your attention. They work a bit different because in that
version of JavaScript, there wasn't a self-replicating array
object like the kind available to more recent version (starting
with JavaScript 1.2). To create the equivalent to an array with
this version of the language, you need to first create and
instance of the Object() object and name it. You would name it
something descriptive, of course. Once created, you may assign
to the Object object the properties you require using the [ ]
operators to stuff values into the object. You must keep track
of the length of the array on your own - this version of
JavaScript doesn't recognize the length property of the more
recent versions. By assigning a length property to the object
and assigning a value to it, you may be able to return the
length of the array. The downside to this workaround is that the
newly created length property will be an item of the array and
occupy the number one position. Since the Zero Based Index
method is used, length will be in position [0]. Examine the
example below.
var arrayStuff = Object();
arrayStuff.length = 3
arrayStuff [1] = " red";
arrayStuff [2] = " green";
arrayStuff [3] = " blue";
document.write("The contents of the array are : " +
arrayStuff[1] + arrayStuff[2] + arrayStuff[3])
The example shows first the creation of a new Object() object.
The first position of the hypothetical array is taken by the
length property, which is set to 3. The rest of the array is
created with the values of red, green, and blue - which are
strings because they're within quotes. Referencing of the array
contents start at position [1] instead of position [0] because
the length property occupies position [0]. You would reference
the array in the same manner as in JavaScript 1.2, as shown
within the document.write statement. Simple. The output of the
above example is shown below.
The contents of the array are : red green blue
Now since we included a length property in the example, we might
as well use it. Examine the following variation of the above
example which utilizes the length property within a for
statement (which you'll learn more about eventually - be
patient).
var arrayStuff = Object();
arrayStuff.length = 3
arrayStuff [1] = " red";
arrayStuff [2] = " green";
arrayStuff [3] = " blue";
document.write("The contents of the array are : ");
for (n=1; n<=arrayStuff.length; n++) {
document.write(arrayStuff[n], " ");
}
The example shows the use of the length property of the
arrayStuff object being used within a for statement. The
conditional statement as the condition of the for statement,
which is within the brackets, takes the value of the length
property and increases it by one. This is your first instance of
seeing a loop function. The initial value is 1 because the
length property is in position 0 within the array - arrays are
zero based indexes. The number of the index is represented by
the letter n which initially has a value of one as defined by
the "n=1" statement. This value of n is then referred to the
arrayStuff.length property with the "n<=arrayStuff.length"
statement. Finally, the value of n is increased by one with the
"n++" statement using the "increase by one" JavaScript operator.
Within the opening and closing braces of the for statement is a
document.write statement which calls upon the condition within
the brackets of the for statement. The position within the array
is represented by the letter n within the square brackets,
telling the browser to interpret the condition within brackets
until it runs out of items in the arrayStuff array. The results
are written to the screen and should look as follows.
The contents of the array are: red green blue
That's it for arrays. You now have the knowledge required to
advance on to the more in depth JavaScript statements such as
conditional expressions and loops. Variables and arrays are used
extensively in these operations. Next week The JavaScript Chronicles
covers Operators.
The Length Property
JavaScript Introduction
JavaScript Operators
The JavaScript Chronicles
JavaScript Introduction
Part 2: Data Types
Part 3: Arrays
Part 4: Operators
Part 5: Conditional Statements
Part 6: JavaScript Functions
Part 7: Pattern Matching - The RegExp Object
Part 8: Introduction to Server Side JavaScript
Part 9: Server Side JavaScript Mail Sending
Part 10: Server Side JavaScript and File Manipulation
Part 11: Working with Forms in JavaScript
Part 12: Getting to Know Dynamic HTML
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